As is known, the yarns needed to form knitting, in knitting machines for hosiery and the like, are supplied to the needles of the machine by way of suitable yarn fingers which are arranged laterally to the needle holder at a feed or drop of the machine.
At a feed or drop there are usually a plurality of yarn fingers, which can be actuated simultaneously or alternately so as to supply a plurality of yarns to the needles and/or vary the yarn or yarns supplied to the needles that pass at such feed or drop as a consequence of the motion of the needle holder with respect to the yarn fingers.
In many cases, each yarn finger is constituted substantially by an elongated body which is pivoted, with an intermediate portion of its longitudinal extension, to a supporting block and extends, with one of its ends, or yarn dispensing end, toward the needles arranged in the needle holder. The yarn finger can rotate on command, through an angle of preset breadth, about its own fulcrum with respect to the supporting block in order to pass from an inactive or off-work condition, in which it is spaced with its yarn dispensing end from the needles of the machine to prevent the needles, at the feed being considered, from being able to take the yarn dispensed by the yarn finger, to an active position, in which it is closer, with its yarn dispensing end, to the needles so that the needles, which are actuated at the feed being considered, can take the yarn to form new loops of knitting.
The need to be able to perform different types of knitting at a same feed or drop of the machine has highlighted the need to be able to have different positions for the dispensing end of the yarn fingers. Such different positions require, for the actuation of a yarn finger, the adoption of different actuators, which increase significantly the complexity of the yarn finger and of the elements designed to support and actuate it. Moreover, the presence of a plurality of actuators for the actuation of a yarn finger causes problems during design, since it is difficult to combine the requirements of space occupation imposed by the adoption of a plurality of actuators with the space available at a feed or drop of the machine.
In order to solve such problems, a device for feeding yarn to knitting machines for hosiery or the like has been proposed which is disclosed in Italian patent 1.325.202 by the same Applicant.
Such device comprises a supporting block, which can be associated with the machine laterally with respect to the needle holder and supports, for each yarn finger, an intermediate element which can rotate, with respect to the supporting block, about a first axis which is oriented substantially parallel to the tangent to the trajectory of the motion of the needle holder with respect to the supporting block. The intermediate element supports, so that it can rotate about a second axis which is substantially parallel and spaced with respect to the first axis, a corresponding elongated yarn finger, which is arranged substantially horizontally and protrudes from the block toward the needle holder. The yarn finger is pivoted, with an intermediate portion of its longitudinal extension, to the intermediate element about the second axis. By way of first and second actuation means, which act respectively on the intermediate element and on the yarn finger, causing their rotation through arcs of adjustable breadth, about the respective rotation axes, the position of the yarn dispensing end of the yarn finger is changed in order to meet the feed requirements of the needles during the several steps of the knitting of the machine.
Although this device has undeniable advantages in terms of versatility of use and precision in feeding the needles, as well as in terms of simplicity of construction and actuation, it suffers some drawbacks.
One of such drawbacks consists in that since the supporting block with the several yarn fingers faces the needle holder laterally, it conceals and hinders access to the work region of the needles, complicating the operations for threading the yarn in the yarn fingers and for adjusting the position of the yarn fingers with respect to the needles in machine tuning operations.
Another drawback consists in that the yarns, in their path from the inlet to the outlet of the feeder, undergo changes in direction with angles of considerable breadth, which increase the frictions that contrast the sliding of the yarns.
A further drawback, which arises from the arrangement of the supporting block and of the yarn fingers with respect to the supporting block, is constituted by the fact that it is not always possible to achieve optimum positioning of the yarn dispensing end of the several yarn fingers in relation to the position of the needles, particularly when a yarn finger is moved to an off-work position to interrupt the feed of the yarn to the needles.